We Built This Machine For Us
by Eternal Love Song
Summary: A look at the relationship between Midoriya, Shinso, and Hatsume. They may not function as smoothly as others, but their relationship works in it's own way. [Established relationship, Polyamory, OT3, Developing relationship, Character Study, Introspection]


There was a clatter as metal fall from the table and piled onto the floor. Mei didn't pay it any attention. She needed more space on the table and wasn't afraid to clear away anything not immediately in use. If her babies couldn't take a little wear and tear they weren't very good in the first place.

She paused long enough to flex her stiff fingers, absently cracking her neck. She was far too stiff. She'd been hunched over her work bench for a little too long, but there was no chance she would leave until her work was done. Everything was background noise compared to that. The grumbling in her stomach was no worse than the kink in her back, the grim on her flesh was no more than an itch, and the great thing about her quirk was that she could focus even when her eyes became blurry from lack of sleep.

The bang of the door opening only marginally got her attention. She turned to glance at the door, but her attention quickly went back to her work when she saw that it was only Shinso.

"It smells like a pig pen in here," Shinso announced as he crossed the room. "Would it kill you to air out the room every once in a while?"

He propped himself up on the work bench beside her latest project, but she didn't bother to look at him. She needed to focus and Shinso was a distraction.

The silence settled between them for a moment before he tapped on her project. "Tell me about this."

She didn't look up as she began to rattle off information, but found herself stopped halfway through.

"That's great, Mei! Look at me," Shinso ordered. There was a smile on his face, humor in his voice. "Do I even have to say it?" He asked, shaking his head at her. "Go back to your room, take a shower, sleep for eight hours, then call me."

There was no fight in her as she turned to follow his commands.

"Love you, Mei!" His voice followed her out of the room.

* * *

Shinso was with Midoriya when he got the call.

Hanging around both Midoriya and Hatsume had gotten him used to having a near constant stream of noise floating around in the background. Shinso didn't mind it so much. He could tune out if he wanted to and sometimes heard something interesting if he didn't, the only difference was subject matter. With Midoriya it was all quirks, and hero worship, and awkward stories that were way funnier than they had any right to be, even if Midoriya was too embarrassed to see how hilarious he was; and with Hatsume it was tech, and wild ideas, dropped conversations as she inspired herself mid speech. Sometimes the two talked to each other and the combined deluge of noise and ideas was as smooth as music, but he'd never admit to the investment he actually had in them talking.

"Midoriya, be quiet," Shinso commanded. He didn't use his quirk, he didn't have to. Midoriya was the sort of person that defaulted to listening to others anyway, so the chatter that had been going on was slowly halted. Shinso put the call on speaker. "Hi, Mei."

"You're a monster!" Those were the first words out of her mouth. It was something that could easily rub him the wrong way. Words like 'monster' were too close to villain for him to take in stride usually, but he'd learned to give Hatsume a bit more leeway.

Hatsume wouldn't know how to watch her words if she invented a machine to do it for her. She was careless in every sense of the words. The way she spoke, the way she interacted with others, the lack of care she gave herself... It had not taken many days of missed calls, delayed apologies, and forgotten meetups for Shinso to realize that Hatsume was a stable disaster that needed to be taken in stride.

He laughed, leaning back against the bed where he sat on the floor of Midoriya's room. Midoriya moved to sit on the edge of the bed, closer to him. "You sound well rested."

"I was almost done! I was so close."

"You went to see Hatsume?" Midoriya asked. He was smiling, Shinso could hear it.

"I needed to air her out," He explained.

Midoriya laughed, prompting Shinso's smile to become wider.

"I was three upgrades from finishing and you made me forget half of my plans!" She exclaimed. Listening Hatsume complain about having to take care of herself was honestly one of Shinso's secret pleasures.

"You should take better care of yourself, Hatsume," Midoriya told her in the sadly caring tone that made Shinso think he'd make a great hero. He'd perfected that 'I'm not mad, just disappointed voice.' "If you did, Shin would have to show up to make you all the time."

Shinso blushed at the nickname, slumping down in his seat to hide his embarrassment. "Y-yeah, stop being such a pig."

"I'm going to lock you out of my lab. You're banned, you here me!" Hatsume proclaimed.

"Ooh, I'm so scared. Pffft!"

"Hatsume, you know we care about you," Midoriya said, trying to soothe over Shinso's careless response. It made Shinso want to be more flippant, more belligerent, just to see how far Midoriya would go to be a buffer for him.

"If either of you cared about me, you'd let me work!"

She hung up.

Shinso dramatically blew out a long breath and let hid phone drop to the floor. He followed soon after, letting himself fall sideways onto the floor. "You ever wonder what it would be like to have a real girlfriend?" He asked. "One that worries about makeup and dates and dumb stuff like that?"

Midoriya shook his head. "I, uh, I don't think I'd know what to do with myself if Hatsume was someone like that." His face had gone red, like it always did when he talked about relationships, theirs or otherwise.

Shinso lifted his phone and took a picture while Midoriya wasn't looking, quickly gaining his attention from the flash and loud clicking sound. He had his setting perfectly set to embarrass Midoriya whenever he snapped a picture of him. It was swo satisfying to see the panic and red cheeks lighting up Midoriya's face that he took another picture. "Perfect."

There was a chance the Shinso's infactuation with Mei and Midoriya was entirely due to how easily he could troll them both. Shinso grinned.

"Shin, please!" Midoriya launched for the phone, but Shinso predicted that move and held it out of sight.

"Not that easy, Midoriya."

He attempted to get the phone from Shinso a few more times, extending himself further and further until he fell off of the bed and landed on top of Shinso.

"Oof! You trying to kill me, Mido?" Shinso asked.

Midoriya scrambled off quickly. "Oh my gosh, I'm so sorry! I r-r-really didn't mean to!" He was so flustered that he was getting tongue tied.

Shinso laughed as he sat up. "Yeah, I know." He lightly kissed Midoriya's cheek and laughed again as Midoriya's flush covered even more skin. He took another quick pic.

Midoriya groaned. "Shin, why?" He hid his face in his hands as he let himself fall to the floor and curl up in a ball.

Shinso moved over him to snap more pictures. "Hold that pose."

"Hatsume is right. You're a monster."

The tone was so light and playful that Shinso couldn't find himself upset about it. Hatsume could say it. Midoriya could say it. He knew what they meant, what they thought of it. They hadn't redefined the word, just rearranged his feelings about it a bit.

* * *

"Hatsume, is this your room?" Midoriya's jaw dropped as Hatsume held open a door.

She smiled brightly at him. "Yep. Do you like it?"

The room looked more like a junk yard than anything else. There were inventions and spare parts littering every surface he could see, along with a clutter of coffee cups and energy drinks. He found himself looking over at Shinso, who met his gaze with his own skeptical one.

"Do you even have a bed?" Shinso questioned.

Hatsume waved him off as if it was the most trivial thing he could have asked about. "It's in there somewhere. It's not a big deal."

"Is this why you don't sleep?" Shinso continued. "Because your room is a literal landfill?"

"Hey! Don't talk about my babies like they're trash," Hatsume scolded. She took a few careful steps into the room and placed her hand on one of her 'babies.' Something that closer inspection revealed to be a robot that was just slightly shorter than the doorway. "Besides, if I really need to, I can sleep here." She pat the arms which were curled into a craddle position, making Midoriya wonder if she'd been sleeping there the whole time.

Midoriya looked at her with horror. "Is that where you've been sleeping?"

"Midoriya, It's fine," She insisted.

"Nothing about this room is fine!"

"You worry too much."

"I'm not leaving here until this room is livable," He told her.

Shinso let out a breath and moved to lean against the wall across from her door, taking out his phone and sliding to the ground. "I refuse to participate in this."

"That's fine," MIdoriya said, rolling up his sleeves. "I spent a summer cleaning up a beach as quirk training, I can handle Hatsume's room."

"Midoriya, you don't need to do that," Hatsume told him.

"One of us has to and we both know that it won't be you."

"Just sit down and say out of the way," Shinso told her.

"It's my room," She replied, placing her hands on her hips.

"Not anymore it's not."

"Why did you even bring us here to study?" Midoriya asked. "You knew what this place was like."

"I just wanted to pick up something, but I forgot what it was," She admitted.

"You're a fucking disaster, Mei!" Shinso complained loudly.

"Shut up, Shins-"

"Help Midoriya clean your room," He ordered.

Immediately, Hatsume hunched over and began to gather up the empty coffee cups.

Midoriya looked over his shoulder to smile at Shinso. "Thanks."

Shinso gave a thumbs up but kept his eyes trained on his phone. This was going to be a long day and he was pretty sure that no studying was going to get done.

* * *

Hatsume wasn't good at taking care of people, caring about them, interacting with them, or remembering them. She spent long stretches of time locked up in a creative haze, forgetting to call or check on anyone and generally being reclusive until someone came to flush her out. She said the first thing that came to mind which had the effect of making people respond less than favorably to her sometimes.

In the beginning, Midoriya seemed to be hurt by her lack of contact. He'd come peaking into her lab with a sheepish expression and hunched shoulders, which she only noticed because she was so enthusiastic to create something for him that he got nearly all her attention when he showed up. Shinso was usually pissed and they'd ended up screaming at each other when he showed up to vent his rage at her neglect, evolving from indifference on her part to annoyance and anger when he started insulting her skills and abilities.

Eventually Midoriya figured out that she wasn't bothered by his presence and was just forgetful and Shinso stopped taking her long silences so personally. Even as friends Hatsume was a load on their relationship and she wasn't sure why Midoriya put up with her. No one else ever did. Usually after enough missed dates, unanswered calls, and silent visits ass he worked instead of interacting, people gave up on her.

Not Midoriya.

As soon as he realized that she wasn't ignoring him or opposed to his presence, he started showing up with more frequency. He had the patience of a saint. He came to ask her if she needed anything, he didn't stress her about missed appointments, and was actually pretty good company. It was only natural that eventually she'd notice that Shinso kept hanging around the lab, that food appeared on the table at her elbow, that she had pretty consistent friends and felt like a real heel for the way she treated them.

Hatsume knew very well that she sucked at people.

She had her own way of trying to take care of the people she cared about though. Like trying to offer MIdoriya things that could help him control his quirk. Like keeping a space clear floor Shinso when he wanted to show up, somewhere out of sight of the door so that no one else could find him if he didn't want to be found. Like looking up when the door opened so that she could acknowledge their presence.

She wasn't really sure that she was doing enough until Shinso confessed to her on Midoriya's behalf. Apparently, he'd told her that he liked her days earlier and she hadn't realized, so Shinso came into say the same thing in a more blunt manner. That was the dynamic that they shared, had been sharing, when they extended an invitation to include her whatever it was they shared.

Hatsume hadn't known they were... anything, if she were honest. She hadn't paid attention. She never paid attention to anyone, really, except them. She had been pretty sure she would say no up until the point where she'd said yes. Then Midoriya sneaking in to check on her turned into Shinso forcing her out of the lab to eat and sleep, turned into him and Midoriya double teaming the inventions she made to stall them, turned into Shinso using his quirk on her once he learned it was okay.

Hatsume was not good with people. That was why she talked to Shinso about their relationship before Midoriya. Midoriya was better at explaining things, but Shinso was better at actually talking. That was why she let Midoriya lure her out of her lab to hang out.

Hatsume was bad with people, but she could learn and she could be taught.

* * *

They were on the floor of Midoriya's room. It was where they ended up most often, since Hatsume's room was a dumpster fire and Shinso hated having people in his space most of the time despite being fine existing in theirs. He was laying on the floor scrolling through his phone, she was sitting against the wall tinkering with something in the palm of her hand, and Midoriya was sitting on his bed. There was a hum of chatter, but he wasn't sure which of them was doing the talking this time.

Shinso would admit to a lack of planning on his part when he dropped his phone and asked, "Are we ever gonna make out?"

Midoriya made a choking sound from the bed and looked at Shinso with wide, panicked eyes. Shinso had honestly just asked the question without thought, so he hadn't anticipated Midoriya's reaction despite the fact that it was completely obvious. "W-what?"

"Sure," Hatsume shrugged. Leave it to her to not even look up from her current project. "Could be an intriguing course of action."

Shinso rolled over so that he could watch Hatsume. "Are you even into kissing people or are you only attracted to science and robotics?"

Hatsume shrugged. "I've never kissed anyone before, so I don't know."

"W-what?" Midoriya repeated.

Shinso looked over at Midoriya, a grin slowly spreading over his lips at the look on Midoriya's face. "You've thought about it, right?"

"I-I-I... y-you..." His words devolved into a groan and he buried his face in a pillow.

Hatsume actually looked up at this. "You okay, Midoriya?"

"Do you wanna go first?" Shinso added.

"How can you ask me that?" Midoriya yelled.

"Easily."

Midoriya made a strangled sound of embarrassment.

Shinso wasn't sure whether or not those sounds were meant to be words, but it got a chuckle out of him anyway. He moved into a sitting position. "I'll go first."

Midoriya's head popped up from where it was buried. He was completely red, expression utterly mortified, and yet his eyes were glued to both Shinso and Hatsume. Midoriya was so easy to read. Shinso winked at him just to see the embarrassment rise within him.

Hatsume put down her project and looked between them. She stretched her arms out over her head. "We doing this?"

"Yeah," Shinso said."I'm clearly the only one with any experience between us, so I'll take the lead for you hopeless youths."

"Have you k-kissed anyone before?" Midoriya asked.

"Nope," Shinso replied, popping the p and drawing the word out. "But I know more about it than either of you, obviously."

"Teach me, Shin," Hatsume said. She reached out to him, but didn't move, looking more curious than anything else. Shinso rolled to his feet and crawled over to Hatsume, taking her face into his hands. "Don't bite me or anything weird like that."

"Why do you expect me to do something weird?" She asked.

"Because yo always do," He told her. He leaned forward to press his lips to hers and Hatsume surged forward, knocking them both to the ground but keeping their lips connected the whole way. Once they hit the ground she started licking his lips, but more like she was tasting him than trying to do anything sexy. "What the hell, Mei?" He asked, pushing her face away to avoid being licked like she was a puppy.

"What? I didn't bite you?" Hatsume replied.

"No, you did something weird!"

"How was I supposed to know it was weird?"

"Do you usually go around licking people?"

"Well, not anymore," She said.

"The fuck, Hatsume?"

"Y-you... really don't know much about kissing, do you?" Midoriya spoke up quietly.

Hatsume shrugged. "I know the basics. Lips, tongue, and teeth in different arrangements."

"Oh my god, Hatsume," Shinso sighed. "Couldn't you have just followed my lead?"

"What would I learn by doing that?" She asked. "Experimentation is the only way to-"

"I'm not one of your inventions!" He groaned.

Hatsume shrugged. "I could-"

"Please don't say whatever it is that you're thinking. I know that I'm not going to like it." He pushed her away so that he could sit up. "Midoriya, please. I have to show this weirdo what she's supposed to do!"

"Uh... I, um..."

"Midoriya, don't pass out on me. It's just a kiss." Shinso sighed, pulling his legs up and resting his head on his knees. "Why am i dating you two hopeless idiots."

"Beats me," Hatsume replied easily.

"I-I c-could... um, I could t-try..." Midoriya stammered.

"I'm not gonna peer pressure you into a kiss," Shinso told him.

"I-I didn't mean-"

"Midoriya, shut up." Shinso ordered. He used his quirk just to be on the safe side. He wanted to mope, not to guilt trip his partners. Midoriya didn't always see the distinction and it was better not to let him talk himself into doing things he didn't want to make other people happy.

There was a short, blessed silence and Shinso mourned when Hatsume broke it. "You should let me study your quirk some more."

Shinso let himself fall to the ground. "I'm gonna die a virgin."

It was probably a good thing that Midoriya couldn't react to that, because Shinso was certain that statement would have killed him.

* * *

Affection was a difficult thing to get used to between them. Midoriya himself wasn't exactly opposed to the idea, though intimacy made him nervous, once he had time to get used to each new stage in their relationship, he managed not to freak out as much about it. He had stammered for five minutes straight the first time Hatsume held his hand, only to realize that she hadn't meant it that way. It had startled him the first time Shinso hugged him only to later realize it was so that Shinso could flip off people that were staring at them without him being the wiser.

In a lot of ways, it was nice not to be dating people that wanted to be all over him all the time. In other ways, it was a little disappointing and frustrating.

Hatsume never initiated touching unless it was for the purpose of some experiment, wanting to study his quirk, or trying to get him to participate or help her with an invention.

Shinso was as likely to touch him as not. He wasn't big on public affection, but would get more touching if there were people around that he could annoy or piss off with it the action. He would put an arm around Midoriya to show him something on his phone or hold his hand on rare occasions, but most public affection was not initiated. Sometimes Shinso would lean against him when they were in Midoriya's room and that was nice, but it wasn't exactly what he wanted. He didn't know what he wanted or how to express the desire that nagged at him.

It was for this reason that Midoriya was totally surprised that the first kiss he shared in this relationship was with Hatsume.

"Hey, Midoriya, sit here." She cleared a space on her work bench and pat the area to indicate where she wanted him.

"What's this for?" He asked as he hopped into place.

"Shinso got me thinking and I feel like we should conduct our own experiment," She told him.

"What experiment?"

Hatsume took his face in her hands, staring at him intently and mumbling her observations out loud. She turned his head left and right, up and down, looked into his eyes and closely at his lips.

"Uh, Hatsume?"

"Shh. You'll interrupt my notes, Midoriya."

"Are you recording this!" He asked, eyes darting around to search for a watching camera.

"Audio only," She replied. "Now shh. Subject seems anxious, mostly likely due to the surprise of preservation rather than the soon to precede activities."

"What acti-"

She pressed her lips to his, soft and warm and nothing like what she'd done to Shinso weeks ago. He was blushing, a warmth spreading throughout his entire body when she pulled away. "H-Hatsume..."

"Pleasant. Receptive," She said clearly. "First experiment a success. Now to explore the variables."

"Wha-"

Her mouth closed down on his once more, except this kiss was nowhere near as simple and Midoriya had the sudden thought that she had much more experience than she had a few weeks ago.

* * *

Watching her boyfriends sparring was something that she never thought she would find as interesting as she did. On a surface level there was interest, of course. Having the chance to study Midoriya's quirk in action was always something she was interested in, and having a controlled environment to observe Shinso was something she constantly fought for. This was different though.

They didn't always or even most of the time, spar using their quirks. Most of the time it was Midoriya running through simple motions, demonstrating kicks and punches, and Shinso reluctantly trying to imitate the actions. Shinso liked to complain a lot about being 'forced to train' but she was almost certain he was the one that asked Midoriya for help and he tried to push himself in training like he never did anywhere else.

She wasn't always sure why she showed up to watch these training sessions. Sometimes she participated. She wasn't exactly trying to be a hero like they were, but staying in shape made some things easier for her. Watching them was oddly compelling. Studying the movement of their bodies, the subtle muscle spasms, watching the sweat drip down their skin.

"Oh!" Her exclamation caught both boys attention and paused mid movement to look at her. "I find you both attractive."

Shinso immediately began laughing, putting his hands on his knees to brace himself as his breathing was replaced with a constant stream of giggles.

Midoriya turned red, arms self consciously covering his body."Wh-what m-m-made you..."

"Hastu... Hatsume... Oh god," Shinso tried to speak between fits of laughter with little success at first. "Holy shit... Only you, Mei."

"Um..." Midoriya looked nervous, fidgeting in place and unsure of what to say.

Hatsume was pretty sure she knew how to smooth over this situation. She smiled at them. "Hey, Shinso? I think now would be a good time for that making out that you wanted to do before."

"Ha-Hatsume!" Midoriya yelled.

"This is isn't the first time we've kissed Midoriya, it's fine," She told him.

"B-but..."

"Unless you don't want to?" She questioned.

He blushed more and avoided her eyes, then Shinso's as Midoriya noticed him watching as well. "I... I do... want to," He admitted quietly.

"Then there's no problem," Shinso said. He reached out for Midoriya's hand, pulling him closer and smiling softly. "Let's go to my room, for once. Less interruptions."

Midoriya nodded shyly.

Hatsume stood up, dusting off her pants, and took Midoriya's other hand. She smiled at him enthusiastically. "I think this will go well. Don't be so nervous. I already studied this extensively-"

"That's probably not helping, Mei," Shinso told her.

"Does my excitement help?" She asked. "Because I think I'm fairly excited."

"That's a nice change," Shinso said. "I'm pretty excited too."

It was quiet for a while Midoriya added, "Y-yeah... so am I."

She and Shinso smiled at each other. It wasn't the smoothest relationship, but it seemed to work for them and they all enjoyed it, so she looked forward to gathering all the data about their habits and likes as she could.


End file.
